use uint64_t for cycles and average calculation

Makefile

@@ -8,7 +8,7 @@ LDFLAGS := -luring -pthread -lrt
 CFLAGS := -Werror -Wall -g -O3
 # CFLAGS := -Werror -Wall -g -O0
 
-.PHONY: all clean eval docker-eval
+.PHONY: all clean eval docker-eval check
 
 eval: all
 	@for syscall in $(SYSCALLS); do echo -n "$$syscall " ; ./bench-$$syscall; done
@@ -28,6 +28,8 @@ $(foreach syscall,$(SYSCALLS),$(eval $(call generateTargets,$(syscall))))
 clean:
 	rm -f $(OBJ)
 
+check: tidy check-format
+
 tidy:
 	clang-tidy *.c
 

bench.c

@@ -42,8 +42,12 @@ int main() {
 			errx(EXIT_FAILURE, "cycles overflowed at %ld", i);
 	}
 
-	double avg_nanos = nanos_sum / (double)iterations;
-	double avg_cycles = cycles_sum / (double)iterations;
-	printf("%lf ns, %lf cycles\n", avg_nanos, avg_cycles);
+	// Since uint64_t <-> double conversion are not well defined
+	// and we use really small units (cycles and nanoseconds) I am willing
+	// to accept that we throw away anything after the decimal point.
+	uint64_t avg_nanos = nanos_sum / iterations;
+	uint64_t avg_cycles = cycles_sum / iterations;
+
+	printf("%lu ns, %lu cycles\n", avg_nanos, avg_cycles);
 	return 0;
 }

stopwatch.c

 #include "stopwatch.h"
 
-int64_t cycles_start, cycles_stop;
+uint64_t cycles_start, cycles_stop;
 struct timespec start, stop;
 
 int64_t sec_to_nanos(int64_t sec) { return sec * 1000 * 1000 * 1000; }
@@ -13,4 +13,4 @@ int64_t clock_diff_nanos() {
 	return nanos;
 }
 
-int64_t clock_diff_cycles() { return cycles_stop - cycles_start; }
+uint64_t clock_diff_cycles() { return cycles_stop - cycles_start; }

stopwatch.h

@@ -3,17 +3,17 @@
 #include <stdint.h>
 #include <time.h>
 
-extern int64_t cycles_start, cycles_stop;
+extern uint64_t cycles_start, cycles_stop;
 extern struct timespec start, stop;
 
-static __inline__ int64_t rdtsc_s(void) {
+static __inline__ uint64_t rdtsc_s(void) {
 	unsigned a, d;
 	asm volatile("cpuid" ::: "%rax", "%rbx", "%rcx", "%rdx");
 	asm volatile("rdtsc" : "=a"(a), "=d"(d));
 	return ((unsigned long)a) | (((unsigned long)d) << 32);
 }
 
-static __inline__ int64_t rdtsc_e(void) {
+static __inline__ uint64_t rdtsc_e(void) {
 	unsigned a, d;
 	asm volatile("rdtscp" : "=a"(a), "=d"(d));
 	asm volatile("cpuid" ::: "%rax", "%rbx", "%rcx", "%rdx");
@@ -30,7 +30,7 @@ static inline void stop_watch() {
 	clock_gettime(CLOCK_MONOTONIC, &stop);
 }
 
-int64_t clock_diff_cycles();
+uint64_t clock_diff_cycles();
 int64_t clock_diff_nanos();
 double nanos_to_millis(int64_t nanos);
 int64_t sec_to_nanos(int64_t sec);